Who's the best trade chip on the summer market? Heck, pick one. Between Johnny Cueto, Cole Hamels, David Price, Justin Upton and Carlos Gomez, there are plenty to choose from.

But none of them is the market's most interesting trade chip. That title belongs to Mark Appel.

As of now, the hard-throwing right-hander is still property of the Houston Astros. They drafted Appel out of Stanford with the No. 1 overall pick in the 2013 draft, and his recent promotion to Triple-A Fresno puts him...